Aim-To determine the number of missed points on frequency doubling technology (FDT) perimetry that optimise the sensitivity and specificity of the test and to determine the topographical accuracy of the test in a clinical setting. Methods-In a prospective study, the perimetric data from 99 patients who underwent both FDT perimetry in the screening mode and Humphrey 24-2 (H24-2) were used to determine the sensitivity and specificity of the FDT perimetry compared with the full threshold H24-2 as the gold standard. Results-Missed points on the FDT perimetry correlated with both the mean deviation and the corrected pattern standard deviation on the Humphrey perimetry. A score assigned to abnormal points on the FDT perimetry and the Humphrey total deviation plot showed a significant correlation for both the location and the depth of the defect. In comparing the Humphrey hemifield test with the FDT perimetry results, if at least one missed point on the frequency doubling test was considered as abnormal then the overall sensitivity of the test was 78.1% and the specificity was 89.1%. Conclusion-FDT perimetry in the screening mode performed in a clinical setting was highly specific, exhibited reasonable sensitivity, and accurately determined the location and depth of scotomas when compared with the full threshold Humphrey 24-2. (Br J Ophthalmol 2001;85:360-362) Frequency doubling technology is a relatively new method of visual field testing that relies on an optical illusion first described by Kelly in 1966.1 The anatomical substrate of this eVect has been ascribed to the retinal ganglion cells (RGCs), 2 which are thought to be particularly susceptible to early glaucomatous damage. This has led to the development of frequency doubling technology (FDT) perimetry with particular use as a glaucoma screening tool. 5-7Preliminary results suggest that FDT perimetry is a rapid, valid test for glaucomatous field loss. 8-16In a clinical study of glaucoma suspects, Quigley 8 found a sensitivity and specificity of over 90% compared with Humphrey full threshold perimetry. Other investigators have recently corroborated the high specificity but have reported a lower sensitivity. 14-16Although preliminary results are impressive, the optimal interpretation of FDT perimetry data is unclear. Further clinical data are needed before this test can be confidently and accurately applied in clinical practice. Furthermore, there are limited data on the topographical accuracy of FDT perimetry.We conducted a prospective clinic based study comparing FDT perimetry with Humphrey 24-2 (H24-2) perimetry in a consecutive series of patients who were attending our glaucoma clinic. We determined the number of missed points on the FDT perimetry that optimised the sensitivity and specificity of the test in screening mode and determined the ability of FDT perimetry to localise the location and depth of a scotoma. MethodsAll patients involved in the study were attending the glaucoma service at the Stoke Mandeville eye unit, as either a review or a ...

SummaryRoth spots (white-centred retinal haemorrhages) were classically described as septic emboli lodged in the retina ofpatients with subacute bacterial endocarditis. Indeed many have considered Roth spots pathognomonic for this condition. More recent histological evidence suggests, however, that they are not foci of bacterial abscess. Instead, they are nonspecific and may be found in many other diseases. A review of the histology and the pathogenesis of these whitecentred haemorrhages will be provided, along with the work-up of the differential diagnosis. How is it that such diverse conditions produce retinal haemorrhages of the same morphology? Excluding patients with systemic sepsis, it is inconceivable that the white centres in all the other cases represent infected embolic foci of septic infiltrates. Furthermore, with the exception of patients with leukaemia, it is difficult to imagine that these lesions represent a concentration of leukocytes. Conditions in which RothThe answer lies in a closer histological examination of the white centre of the Roth spot. Histopathology of the Roth spotEarly investigators were surprised by the lack of definite aggregations of bacteria and leukocytes in the white centre of the lesions in specimens of patients who died of sepsis.4 Instead, they observed areas within the lesions where cellular staining is faint and the endothelium of capillaries becomes indefinite and shows hyaline changes. These histological observations were inconsistent with the proposed explanation of a bacterial abscess as the white centre of a Roth spot. Recent investigators have given prominence to the presence of fibrin in the lesions. Wong and Bodey had noted fibrin in their aplastic anaemia patients.' Von Barsewisch observed in perinatal retinal haemorrhages that the electron microscopic appearance of white-centred haemorrhages corresponds to fibrin fibrillae and concluded that the white centre of Roth spot represents a fibrin thrombus at the site of a vessel rupture.6 Duane et al confirmed the observation of the fibrin and platelet aggregate in the white centre of Roth spots in leukaemic patients and further alluded to the fact that the haemorrhage in one leukaemic eye came from a centrally located aneurysm, with 'symmetrical distribution of fibrin, platelets and infiltrating red blood cells' arising from the aneurysm.7The pathogenesis of Roth spots: a unifying theory White-centred haemorrhage may thus result from the rupture 6f retinal capillaries and the extrusion of whole blood. Subsequent platelet adhesion to damaged endothelium and the platelet release reaction initiates the coagulation cascade on 11 April 2019 by guest. Protected by copyright.

Summary: Cerebral blood flow was measured by the Hz clearance method 30 and 60 min after the implantation of 300, 250, 125, or 50 !--l m diameter platinum-iridium elec trodes 2 mm deep into the right parietal cortex of normo thermic, normocarbic halothane-anesthetized rats. An other group of animals had 50 !--l m electrodes inserted I mm. In all animals, the presence or absence of a wave of spreading depression (SD) was noted at the time of im plantation, with recordings made with glass micropi pettes. H2 flow values were compared with those mea sured in gray matter from the same anatomical region (but from different rats), using [ 3 H]nicotine. The incidence of SD ranged from 60% following insertion of 300 !--l m elec trodes to 0% with 50 !--l m electrodes. H2 clearance flows also varied with electrode size, from 77 ± 21 ml 100 g� 1 min � 1 (mean ± standard deviation) with 300 !--l m elec trodes to 110 ± 31 and 111 ± 16 ml 100 g� 1 min� 1 with 125 and 50 !--l m electrodes, respectively (insertion depth of 2 mm). A CBF value of 155 ± 60 ml 100 g� 1 min � 1 wasThe hydrogen clearance method for the measure ment of CBF offers several advantages over other techniques. It permits the simultaneous determina tions of local CBF in multiple sites. These measure ments can be repeated many times over periods ranging from hours to days. The method is also technically simple to perform and requires rela tively inexpensive equipment. However, in spite of the widespread use of this technique, questions re- garding its validity have been recently raised. It has been known for many years that in spite of good correlations between CBF values determined by H2 clearance and other flow measurement methods, the absolute values obtained with H2 clearance are often lower than those obtained with other tech niques. For example, Furlow measured CBF of 80 ml 100 g � 1 min � 1 in the rostral neocortex of awake (but paralyzed) rats using implanted 200 /-lm diam eter platinum electrodes (Furlow, 1982). In con trast, using e 4 C]iodoantipyrine autoradiography, a flow of 139 ml 100 g -1 min -1 was obtained for the same area (in a separate group of animals). More importantly, Tomida et al. measured regional CBF in gerbils by H2 clearance (using a 250 /-lm diameter electrode) and by either eH]nicotine or

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